Phase unbalance meter



Jan. 19, 1937. G. STARK 2,068575 PHASE UNBALNCE MEIER Fil6d 0ct. 17, 1934 Fig.l.

Geor*% Stark,

His Afitorneg.

Patented Jan. 19, 1937 UNITED STATES PATENT OFFICE PHASE UNBALANCE METER ration f New York Application October 17 1934, Srial N0. 748,641

In Germany February 28, 1934 6 Glaims.

My invention relates to apparatus operating in response to voltage phase unbalance and in particular to a meter for integrating the phaseunbalance conditions of power circuits.

In accordance With my invention, I utilize a self-starting synchronous motor which is arranged 00' be operatively energized in response to the voltage phase unbalance under investigation. The motor is arranged to drive a register so as to integrate the tirne during which the phaseunbalance conditions exist.

The features of my invention which are believed to be novel and patentable Will be pointed out in the claims appended hereto. F01 a better understanding o1 my invention, reference is made in the following description 170 the accompanying drawing illustraoing in Fig. 1 one embodiment of my invention for integrating the tim.e of voltage unbalance of a, polyphase power circuit; Fig. 2 illustrates an equivalent modified arrangement for integrating the time of voltage unbalance in a polyphase power circuit; and Fig. 3 illustrates a star-connection of the voltage-unbalance meter- Eng device to a five-phase power circuit.

In Fig. l, there is represented at l, 2, and 3 the lines of a three-phase power circuit where the metering device is connected thereto 120 integrate the time of voltage unbalance. Here I0 represents ehe fie1d core structure of a. single-phase self-starting synchronous motor such as is commonly usecl to drive time devices. This core has a sing1e magnetic circuit. The rotor l! of the motor will be of the usual construction and may, for example, consist of one 01 more washershaped discs of hardened stee1 With a polar bar across one diameter. The field Winding 01": the motor is unusual in that it consists of three sections, l2, I3 and 23, connected respectively across the phases l2 I3 and 23 of the three-phase power supply.

It will be evident that, if the voltage o1": the three-phase supply is balanced and the winding sections I 2, I3, and 23 are sirnilar, 110 resultant flux Will be produced in the field of the synchronous motor and the motor Will remain id1e. I-Iowever, if there exists a phase unbalance for example, by a. partial or complete failure of voltage on one of the phases of the three-phase circuit, a, resultant single-phase fiux Will be produced in the motor fie1d which, if of sufiicient magnitude, Will cause the motor to starb and 130 operate synchronously with such fiux. This resu1tant single-phase flux will, obviously, have a frequency equal to that of the power circuit and have a. magnitude proportional 110 the voltaeephase unbalance. The motor torque and load will preferably be so proportioned as 110 cause the motor to start and run synchronously when a predetermined undesirable degree of phase unbalance exists and to stop for lesser degrees of phase unbalance.

The frequencies of most power circuits are sufflciently constant that they may be us.ed to distribute oime by means of synchronous-motor driven c1ocks, connected thereto. I utilize this timing feature anti cause the motor 130 drive a suitable integrating register represented ab I4, which will then integrate the rotations of the moto1 and thus sum up or integrate the time of undesirable phase unbalance existing on the power circuit. Such a meter will be useful to 1;he power supp1y company to provide a check on the phase balance of feeder circuits supplying single-phase and polyphase 1oads. It will be usefu; to customers as we11 as to the power supp1y company to provide a measure of he time during which a customer undesirably unbalances his polyphase supply circuit, and the measurement may be used when computing the customers povver 10111 to increase 01' decrease the power bi1l in proportion to time of phase unbalance above or below an agreed amount during a, month or on a maximum-demand basis.

In Fig. 2, a modificacion of the invention is represented for measurement of the voltage unbalance conditions of a three-phase circuit hav ing phases I, 2, and 3. Here the three phase voltages supply similar primary windings I6 of a transformer. The Windings 16 are wound on a. common core l! and a secondary Winding l 8 on the same core is thus threaded with any singlephase flux resulting from voltage phase unbalance. One or more self-starting synchronous motor-driven meter devices may then be C011- nected 130 be s.upplied from the secondary Winding i8. This sort of an arrangement Will be desirable for voloage phase-unbalance measurements where it is desirable i;0 have the unbalance integrating device located some distance from the power circuit as it requires only a low-voltage single-phase circuit between the transformer, which Will be located near the power circuit, anal the synchronous driving motor of the phase-unbalance meter. In Fig. 2, a usual form of self-starting synchronous motor I9 is supplied from the seoondary Winding I8 of the transformer and it Will be evident that such motor is energized by a single-phase fiux proportional 110 and equivalent 1:0 that existing in the core l'l of the transformer due to any current unbalance in the power circuit.

Motor I9, in addition to driving a suitab1e register I4, is provided with an electromagnetic brake 2D, the winding of which is connected in series with the motor. 'I'his brake will be ad.- justed so as to respond to a definite current corresponding to a selected degree of phase unhalance. For a phase unbalance below that selected, the brake will be on and the motor will be at rest. This is one means of preventing the motor from operating in response to minor phase-unbalance conditions which are not troublesome and which should not be measured with the more serious conditions but which, nevertheless, produce some energization cf the motor that might cause it to continue operating after having been started in response to a more serious condition of phase unbalance.

'I'he voltagesupplied from the secondary winding I8 of the transformer may also be used for operating other devices, such as a time-delay relay 2l for disconnecting seriously unbalanced loads and a signalling device 22 for giving an ala.rm when the condition of unbalance reaches a predetermined amount.

In Fig. 3, I have represented a modification where the power circuit 23 to which the device is connected is a five-phase circuit and the coils 24 on the core 25 of the motor are connected in star instead cf delta as in Fig. 1. Fig. 3 also shows that the core 25 may, in addition supplying a resultant single-phase flux for operating the motor, be used as a transformer core to supply energy through a secondary coil 26 to a distant phase-unbalance responsive device, such as a meter, re1ay, or signal indicated at 21.

In this modification, the motor has an induction motor secondary rotor 28 and is provided with a load consisting of a dlsc 29 of conduct- Ing material rotating in the field of a permanent magnet 30. The speed of this metering device will, therefore, be proportional to the degree of unbalance and the register I4 will provide an integrated xneasurement of all unbaianced conditions.

It will be evident that although the motor of Fig. 3 has five sirnilar energizing coils 24 and is therefore. suitable for a five-phase circuit, it may be used in connection with a lower phase number circuit. F'or example, three of these coils may be energized from a three-phase circult with the other two coils left open and the resulting flux in its magnetic circuit will be proportional to ehe phase unbalance of that circuit just as in Fig. 1.

Such other modifications as will occur to those skllled in the art and as come within the true spirit and scope of my invention are intended to be included within the claims appended hereto.

What I c1aim as new and desire to secure by Letters Patent of the United. States is:

1. A voltage phase-unbalance responsive device comprising a magnetic core having a plurality of coils wound thereon, means for connecting said coils for energization frorn diflferent voltage phases of a polyphase circuit without phase distortion such that no flux is produced in the core when said coils are energized (man a balanced polyphase clrcuit and so that a resultant single-phase flux independent 013 the direction but proportional to the degree of voltage unbalance exists in the core when said coi1s are energized from an unbalanced polyphase circuit, an integrating register, and a singlephase motor operated in response to the resultant flux in said core for driving said register.

2. A voltage phase-unbalance responsive device comprising a core structure having a single magnetic circuit, a number of similar coi1s wound on said core, terminals for energizing different coi1s thereof from different Voltage phases of a polyphase circuit such that, the voltages across the coils are in phase with and proportional to the voltages cf such different phases whereby, when energized frorn an unbalanced polyphase circuit, a resultant flux independent of the direction but proportional to the degree of voltage unbalance is produced in said magnetic circuit, and a self-starting single-phase synchronous motor operated in response to resultant flux in said magnetic circuit.

3. A voltage phase-unbalance meter comprising a core structure having a single magnetic circuit, a plurality of similar coils wound thereon having terminals for connection to diflerent voltage phases of a polyphase circuit such that said coils will be energized in phase with and in proportion to the phase voltages of such polyphase circuit, a single-phase se1f-starting synchronous motor connected so as to be operated in response to any resuitant flux in said magnetic circuit above a predetermined magnitude, and a counter driven by said motor fo1' integrating its operation.

4. A voltage phase-unoalance meter for polyphasc circuits comprising a magnetic core structure having a sing1e magnetic circuit, a number of simi1ar exciting coils wound thereon, means for respectivcly energizing said coiis from and in proportion to the voltages of the different phases of a polyphase circuit without phase distortion, a single-phase self-starting synchronous motor connected to be energized in response to the flux in said core structure, and means Tor preventing the operation of said motor when the flux in said core structure 1's be1ow a predetermined amount.

5. A voltage phase-unbalance responsive device for polyphase circuits comprising a single i magnetic circuit core structui'e, a nurnber of similar coi1s wound thercon, means for respectively energizing said coils from and in proportion to the voltages of the difierent phases of a polyphase ci1cuit without phase distortion, an

air gap in said magnetic circuit, and a rotor of a single-phase self-starting synchronous motor in said air gap and responsive to the flux there in, said core structure constituting a stator fie1d structure for such motor.

6. In combination With a polyphase power circu1t, means for integrating the time during which the voltage of said polyphase circuit is unbalanced comprising 1egister and a singlephase self-starting synchronous motor for driv ing said register, said motor having similar pri- Inary energizing coils energized respectively irom the difierent voltage phases of said polyphase circuit without phase distortion.

GEORG STARK. 

